Article of manufacture and process of making the same



Patented Dec. 23, 1941 ARTICLE OF MANUFACTURE AND PROCESS OF MAKING THESAIWE Frank H. Reichel, Fredericksburg, Va., assignor to SylvaniaIndustrial Corporation, Fredericksburg, Va., a corporation of VirginiaNo Drawing. Application October '7, 1939, Serial No. 298,399

8 Claims.

The present invention relates to a process of producing tubing and to anarticle of manufacture so produced. More particularly, it relates to aprocess of producing cellulosic tubing and an article so produced, forexample, a tubing adapted for use as sausage casings or to be cuttransversely into short bands and used as shrinkable closures forcontainers.

Tubing cut into short bands is frequently used for container closures ofthe secondary type. For example, it is the usual practice at the presenttime to place short sections of cellulosic tubing over the necks andstoppers of bottles containing beverages, medicines and othersubstances. Since these closures must be economically produced, it isnecessary that they be produced rapidly, and due to the fact that theyare frequently required to be transparent in part or in whole, or to besuitably colored, it is necessary that the cellulose tubing be clear andfree from deposits of materials which would render them cloudy andunsightly. Such bands must also have a high wet and dry strength andshow a substantial transverse shrinkage on being dried;

In the manufacture of tubing for use as container closures heretofore,several serious obstacles have arisen. The material from which thetubing has been manufactured has usually been viscose. When viscose isextruded in the form of a tubing into a coagulating bath containing acoagulating substance which does not regenerate the viscose, forexample, ammonium sulfate, the rate of coagulation is extremely slow andthereby renders the production of such tubing expensive because theapparatus must be very long or the rate of extrusion very slow. When theviscose is extruded into a coagulating bath which also regenerates theviscose, for example, sulphuric acid, although the rate of coagulationand regeneration is rapid, the tubing is invariably cloudy due to theformation of large amounts of opaque substances in the tubing, andgaseous products have been formed at such rate as to greatly exceed thecapacity of the tubing.

Many attempts have been made .to overcome the above mentioned obstacles,as by providing facilities for withdrawing the gas from the interior ofthe tubing through the extrusion nozzle. This has been generallyunsatisfactory due to the fact that coagulating liquid is frequentlyinjected into the interior .of the tubing at the point of formation, andit has been impossible to withdraw the gas without at the same timewithdrawing substantial quantities of the coagulating liquid, and wherethe tubing passes under a roller the gas will be trapped by the liquid.A further attempt has been made to pass the tubing out of theregenerating bath at intervals so as to permit the gas to diffusethrough the wall'of the tubing and escape into the atmosphere. This hasnecessitated the use of complicated machinery and the rate of diffusionis not controllable so that it was impossible to definitely provide forthe escape of the gas.

The third approach, which has been the on most generally used, has beento slit the tubing at frequent intervals to permitthe escape of the gas.This has been wasteful of the tubing since that portion of the tubingcontaining the slit was, of course, not usable.

The present invention overcomes all of the foregoing obstacles and makesit possible to rapidly and economically produce an excellent grade oftubing.

It is an object of the present invention to provide a method of rapidlyand economically forming tubing of thetype capable of use as ashrinkable container closure.

It is another object of the present invention to provide a process ofproducing tubing without the formation of excessive quantities of gas soas to avoid the necessity for slitting the tubing at frequent intervals.

It is a further object of the invention to pro vide a process ofproducing tubing in which the step of coagulating and regenerating theviscose may be carried out simultaneously or independently, as desired,without the formation of an excessive quantity of gas, and thereby avoidthe necessity for slitting the tubing at frequent intervals. g

It is another object of theinvention to provide an improved article ofmanufacture in the form of a tubing capable of use as a shrinkablecontainer closure. 7

It is still a further object of the invention to provide a containerclosure which has increased shrinkage characteristics. a

Other objects and advantages, if .notspecifically pointed out will beapparent from the following detailed description of what is nowconsidered the preferred form of the invention.

The process of the invention comprises extruding in the formof a tubinga composition comprising a cellulose xanthate and a cellulose ether inan alkaline solution into a coagulating bath to coagulate thecomposition and thereby render the tubing shape-retaining. The viscoseis simultaneously with the coagulation or subse quently substantiallyregenerated to cellulose hydrate to complete the hardening of thetubing.

The invention accordingly comprises the several steps and relation ofone or more of such steps with respect to each of the others, and theproduct possessing the features, properties, and the relation ofelements, which are exemplified in the following detailed disclosure,and the scope of the invention will be indicated in the claims.

The cellulose ether employed may be an alkalisoluble cellulose ethersuch, for example, as a cellulose alkyl ether, a cellulose oxy-alkyl,hydroxy-alkyl or carboxy-alkyl ether and salts of carboxy-alkyl ethers,as well as mixed alkyl hydroxy-alkyl ethers or ether-xanthates formed byany of the well known processes which within themselves form no part ofthe present invention and will not be described in detail. The ethersare soluble in aqueous solutions of strong alkalies such, for examples,as sodium hydroxide, potassium hydroxide and quaternary ammonium basesand such alkali solutions may be used for dissolving both the ether andthe cellulose xanthates.

The ratio of cellulose contained in the viscose to cellulose ether mayvary between 3 to 1, to 1 to 2, a ratio of 1 to 1, being the preferredratio. The alkali soluble cellulose ether may be added at any suitablepoint in the manufacture of the xanthate, such as to the xanthate at anytime after xanthation has taken place or to a viscose solution which isproduced by dissolving the xanthate in an alkali solution. From certainaspects of the invention, however, it is preferable.

that the alkali-soluble cellulose ether be added to the alkalinesolution of the cellulose xanthate. The use of cellulose ether with theviscose makes it possible to use a much greener viscose, or one whichhas not been decomposed to the extent usually required to produce ashrinkable container closure, thereby effecting a saving in time anddispensing with the necessity for storage space. The solid celluloseether may be used to make the composition, but preferably the celluloseether is first dissolved in an aqueous alkaline solution of suitableconcentration.

The composition of cellulose xanthate and alkali-soluble cellulose ethermay be formed into a tubing as, for example, by passing the mixture intoany well known type of extrusion head from which it is extruded in theform of a tubing into a coagulating bath. By the use of a composition ofcellulose xanthate and alkali-soluble cellulose ether, it is possible touse a coagulating bath which does not regenerate the viscose, forexample, ammonium sulfate, and the presence of the alkali-solublecellulose ether increases the rate of coagulation to a much greaterextent than is possible when viscose is used alone. The alkalisolublecellulose ether rapidly coagulates and forms a relatively strong gelwhich makes it possible to inflate the tubing to the desired size andpass the tubing over rollers and through the necessary baths withoutdamaging the tubing.

When a non-regenerating bath is used as a coagulating bath, the tubingmay be later subjected to treatment with an acid, for example, sulfuricacid, for decomposing the cellulose xanthate in the coagulated celluloseether gel, without forming a cloudy tubing and producing gases insufficient quantities to make it necessary to slit the tubing atfrequent intervals. By making the run of the tubing of suflicient lengthto permit infiltration of the gas through the tubing, it is possible toavoid slitting of the tubing altogether.

' and gaseous products in large quantities, thereby producing a tubingwhich is clear and transparent, and which does not have to be slit atfrequent intervals to provide for the escape of gas from the interior ofthe tubing.

Suitable pigments and/or dyes may be added to the composition of viscoseand alkali-soluble cellulose ether to produce any desired colorationand/or opacity in the tubing without adversely affecting the operationof the process.

For the purpose of illustration, but not by way of limitation, thefollowing examples of the invention will be given:

Example I v A composition is formed comprising by weight 5 parts ofcellulose ether, cellulose xanthate to provide 5 parts of cellulosebased on the weight of cellulose used in making the cellulose xanthate,1.63 parts of sulfur contained in the xanthate, 8 parts of a causticalkali such as sodium hydroxide and sufiicient water to make 100 partsby weight of the composition. The composition may be formed by addingthe alkali-soluble cellulose ether directly to viscose, which may berelatively green, in the proper proportions to produce the foregoingcomposition, or cellulose xanthate may be added to an alkaline solutionof cellulose ether in the proper proportions to produce the foregoingcomposition.

The composition so formed is extruded into a solution comprising 250grams per liter of ammonium sulfate and 1 gram per liter of sulfuricacid to coagulate the cellulose xanthate and the alkali-solublecellulose ether. The purpose of the small amount of sulfuric acid is toneutralize liberated ammonia and the sulfuric acid may be dispensed withentirely, if such is desired.

Instead of the coagulating solution described above, the composition maybe extruded into a solution comprising 250 grams per liter of ammoniumsulfate and grams per liter of sulfuric acid. In passing through thissolution, both the cellulose xanthate and the cellulose ether will bequicklycoagulated and the cellulose xanthate will be regenerated to formcellulose hydrate. The length of the run of the tubing through the bathneed be only a few feet to accomplish these results. The use of thestronger acid produces a firmer gel and facilitates the manufacture at ahigher speed.

When the bath containing only 1 gram per liter of sulfuric acid is used,the tubing is passed therefrom to a suitable washing bath and then to aregenerating bath, and from there to washing and purifying baths in aknown manner. When the coagulation and regeneration of the cellulosexanthate takes place in the same bath it will, of course, not benecessary to pass the tubing into a separate regenerating bath.

When the product is to be used as a container closure the finishedtubing is severed transversely into bands and the bands suitably packedfor shipment to the consumer.

, alone.

Example 11 Tubing is made as in Example I and the purified product istreated, while in the Wet gel state, with a softening agent such, forexample, as glycerine, diethylene glycol, or a mixture thereof, and thesoftened tubing dried while inflated in a known manner. The dried tubingmay be used as a casing for sausage, ham butts, cheese, frozen fowlcarcasses, and other products.

The use of a composition of cellulose xanthate and an alkali-solublecellulose ether in this invention makes it possible to form a tubingwhich is clear and transparent without necessitating.

the use of expensive and time-consuming desulphurizing steps. The use ofthis composition also makes it possible to rapidly produce tubing by theuse of a coagulating bath which does not regenerate the viscose, or theuse of a coagulating bath which does regenerate the viscose, if desired,without producing gaseous products in sufiicient quantity to make itnecessary to slit the tubing at frequent intervals or to providecomplicated and expensive means for allowing the gas to escape.

An outstanding novel result of the invention arises from the fact thatthe coagulation is sufficiently rapid and the quantity of gas generatedso small that the process may be effectively carried out at greaterspeed or on a shorter machine than was heretofore possible.

The article of the invention is a tubing comprising a non-fibrouscomposition of cellulose hydrate and cellulose ether which swells inwater and shrinks on drying. The tubing of the present invention showsan increased transverse shrinkage from 8 per cent to 10 per cent overtubing formed in the same manner from viscose This makes the tubing ofthe present invention peculiarly useful as closuresfor containers sincethe added ability to shrink makes it possible to cover a large range ofcontainer sizes by the use of a single size of tubing band.

The term composition as used throughout the specification and claims isintended to include both true solutions and compatible mixtures ofcellulose xanthate and alkali-soluble cellulose ethers.

Since certain changes in carrying out the above process, and certainmodifications in the product which embody the invention may be madewithout departing from its scope, it is intended that all mattercontained in the above description be interpreted as illustrative andnot in a limiting sense.

The invention having been described, what is claimed is:

1. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed,comprising continuously extruding in the form of a tubing an alkalinesolution of a cellulose xanthate and an alkali soluble cellulose etherinto a coagulating medium for the cellulose xanthate and celluloseether, and decomposing the xan thate substantially to cellulose hydrateto harden the tubing, said cellulose ether being present in sufiicientamount to enhance the ability of the completed tubing to shrink upondrying and to minimize the formation of gases during the saiddecomposition to a point where frequent puncturing of the tubing torelease the gases is avoided.

2. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed,comprising continuously extruding in the form of a tubing a compositionformed by dissolving cellulose xanthate and alkali soluble celluloseether in an aqueous alkaline'solution into a coagulating me-. dium forthe cellulose xanthate and cellulose ether, and decomposing the xanthatesubstantially to cellulose hydrate to harden the tubing, said celluloseether being present in sufiicient amount only to enhance the ability ofthe completed tubing to shrink upon drying and to minimize the formationof gases during the said decomposition to a point where frequentpuncturing of the tubing to release the gases isavoided.

3. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed,comprising dissolving a given weight of alkali soluble cellulose etherand the amount of cellulose xanthate obtained from the use of the sameWeight of cellulose in the making of the cellulose xanthate in anaqueous alkaline solution, continuously extruding the solution so formedin the shape of a tubing into a coagulating medium for the cellulosexanthate and cellulose ether, and decomposing the xanthate substantiallyto cellulose hydrate to harden the tubing, said cellulose ether servingto enhance the ability of the completed tubing to shrink upon drying andto minimize the formation of gases during the said decomposition to apoint where frequent puncturing of the tubing to release the gases isavoided.

4. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed,comprising dissolving from one to two parts by weight of cellulose etherand the amount of cellulose xanthate obtained from the use of from oneto three parts by weight of cellulose in the making of the cellulosexanthate in an aqueous alkaline solution, continuously extruding thesolution so formed in the shape of a tubing into a coagulating mediumfor the cellulose xanthate and cellulose ether, and decomposing thexanthate substantially to cellulose hydrate to harden the tubing, saidcellulose ether serving to enhance the ability of the completed tubingto shrink upon drying and to minimize the formation of gases during thesaid decomposition to a point where frequent puncturing of ,the tubingto release the gases is avoided.

5. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed,comprising continuously extruding in the form of a tubing an alkalinesolution of a cellulose xanthate and an alkali soluble cellulose etherinto a coagulating bath for the cellulose xanthate and cellulose etherwhich does not regenerate the cellulose xanthate, and then passing thecoagulated tubing into a regenerating bath to substantially regeneratethe cellulose of the cellulose xanthate, said cellulose ether beingpresent in sufficient amount only to enhance the ability of thecompleted tubing to shrink upon drying and to minimize the formation ofgases during the said regeneration to a point where frequent puncturingof the tubing to release the gases is avoided.

6. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed.comprising continuously extruding in the form of a tubing an alkalinesolution of a cellulose xanthate and an alkali soluble cellulose etherinto a coagulating medium for the cellulose xanthate and celluloseether, injecting a coagulant into the in: terior of the tubing tocoagulate the tubing from both the interior and the exterior, anddecomposing the xanthate substantially to cellulose hydrate to hardenthe tubing, said cellulose ether being present in sufficient amount toenhance the ability of the completed tubing to shrink upon drying and tominimize the formation of gases during the said decomposition to a pointwhere frequent puncturing of the tubing to release the gases is avoided.

7. The process of producing tubing capable of shrinking upon drying intoclose contact with an object over or around which it is placed,comprising continuously extruding in the form of a tubing an alkalinesolution of a cellulose xanthate and an alkali soluble cellulose etherinto a combined coagulating and regenerating bath whereby the xanthateand the ether are coagulated and the xanthate is decomposed to cellulosehydrate to harden the tubing, said cellulose ether being present insufficient amount to enhance the ability of the completed tubing toshrink upon drying and to minimize the formation of gases during thesaid decomposition to a point where frequent puncturing of the tubing torelease the gases is avoided.

8. As an article of manufacture, a seamless tubing capable of shrinkingwhile drying into close contact with an object over or around which itis placed and formed from substantially regenerated cellulose and acellulose ether, said cellulose ether being present in suflicient amountto enhance the ability of the completed tubing to shrink upon drying andto have reduced the formation of gases during the manufacture of theseamless tubing in a continuous length to a minimum whereby frequentpuncturing of the tubing to release the gases was avoided and wherebythe completed tubing is free from frequent punctures.

FRANK H. REICHEL.

